Everything about Artery totally explained
Arteries are
blood vessels that carry blood away from the
heart (as opposed to
veins, blood vessels carrying blood toward the heart). All arteries, with the exception of the pulmonary and umbilical arteries, carry oxygenated blood.
The
circulatory system is extremely important for sustaining
life. Its proper functioning is responsible for the delivery of
oxygen and
nutrients to all cells, as well as the removal of
carbon dioxide and waste products, maintenance of optimum
pH, and the mobility of the elements, proteins and cells of the
immune system. In
developed countries, the two leading causes of
death,
myocardial infarction and
stroke each may directly result from an arterial system that has been slowly and progressively compromised by years of deterioration. (See
atherosclerosis).
Description
The arterial system is the higher-
pressure portion of the circulatory system. Arterial pressure varies between the peak pressure during heart contraction, called the
systolic pressure, and the minimum, or
diastolic pressure between contractions, when the heart rests between cycles. This pressure variation within the artery produces the pulse which is observable in any artery, and reflects heart activity.
Anatomy
The anatomy of arteries can be separated into
gross anatomy, at the macroscopic level, and
microscopic anatomy, which must be studied with the aid of a
microscope.
Gross anatomy
The arterial system of the
human body is divided into
systemic arteries, carrying blood from the heart to the whole body, and
pulmonary arteries, carrying blood from the
heart to the
lungs.
Systemic arteries
Systemic arteries are the arteries of the
systemic circulation, which is the portion of the
cardiovascular system which carries
oxygenated
blood away from the heart, to the
body, and returns deoxygenated blood back to the heart.
Pulmonary arteries
Pulmonary arteries are the arteries of the
pulmonary circulation, which is the portion of the
cardiovascular system which carries deoxygenated
blood away from the heart, to the
lungs, and returns oxygenated blood back to the heart.
Microanatomy
The outermost layer is known as the
tunica externa formerly known as "tunica adventitia" and is composed of
connective tissue. Inside this layer is the
tunica media, or
media, which is made up of
smooth muscle cells and elastic tissue. The innermost layer, which is in direct contact with the flow of blood is the
tunica intima, commonly called the
intima. This layer is made up of mainly
endothelial cells. The hollow internal cavity in which the blood flows is called the
lumen.
Types of arteries
Pulmonary arteries
The
pulmonary arteries carry deoxygenated blood that has just returned from the body to the
lungs, where
carbon dioxide is exchanged for
oxygen.
Systemic arteries
Systemic arteries can be subdivided into two types; muscular and elastic; according to the relative compositions of elastic and muscle tissue in their tunica media as well as their size and the makeup of the internal and external elastic lamina. The larger arteries >1cm diameter are generally elastic and the smaller ones 0.1-10mm tend to be muscular. Systemic arteries deliver blood to the
arterioles, and then to the
capillaries, where nutrients and gasses are exchanged.
The Aorta
The
aorta is the root
systemic artery. It receives blood directly from the left
ventricle of the heart via the
aortic valve. As the aorta branches, and these arteries branch in turn, they become successively smaller in diameter, down to the
arteriole. The
arterioles supply
capillaries which in turn empty into
venules. Its the size of waterhose.
Arterioles
Arterioles, the smallest of the true arteries, help regulate
blood pressure by the variable contraction of the smooth muscle of their walls, and deliver blood to the capillaries.
Arterioles and blood pressure
Arterioles have the greatest collective influence on both local blood flow and on overall blood pressure. They are the primary "adjustable nozzles" in the blood system, across which the greatest pressure drop occurs. The combination of heart output (
cardiac output) and
systemic vascular resistance, which refers to the collective resistance of all of the body's
arterioles, are the principal determinants of arterial blood pressure at any given moment.
Capillaries
The
capillaries are where all of the important exchanges happen in the
circulatory system. The capillaries are a single thick cell to aid fast and easy diffusion of gases, sugars and other nutrients to surrounding tissues.
Functions of capillaries
To withstand and adapt to the pressures within, arteries are surrounded by varying thicknesses of
smooth muscle which have extensive elastic and inelastic
connective tissues.
The pulse pressure, for example
Systolic vs.
Diastolic difference, is determined primarily by the amount of blood ejected by each heart beat,
stroke volume, versus the volume and elasticity of the major arteries.
Over time, elevated arterial
blood sugar (see
Diabetes Mellitus),
lipoprotein cholesterol, and
pressure,
smoking, and other factors are all involved in damaging both the
endothelium and walls of the arteries, resulting in
atherosclerosis or
Diabetes Mellitus.
History
Among the ancient Greeks, the arteries were considered to be "air holders" that were responsible for the transport of air to the tissues and were connected to the
trachea. This was as a result of the arteries of the dead being found to be empty.
In medieval times, it was recognized that arteries carried a fluid, called "spiritual blood" or "vital spirits", considered to be different from the contents of the veins. This theory went back to
Galen. In the late medieval period, the
trachea, and
ligaments were also called "arteries".
William Harvey described and popularized the modern concept of the circulatory system and the roles of arteries and veins in the
17th century.
Alexis Carrel at the beginning of
20th century first described the technique for vascular suturing and anastomosis and successfully performed many organ transplantations in animals; he thus actually opened the way to modern vascular surgery that was before limited to vessels permanent ligatation.
Further Information
Get more info on 'Artery'.
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